Tropical Storm HUMBERTO

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TROPICAL STORM HUMBERTO DISCUSSION NUMBER 26
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092013
500 PM AST MON SEP 16 2013
THE DEEP CONVECTIVE CANOPY THAT WAS NEARLY COVERING THE CENTER
EARLIER HAS BEEN SHEARED EASTWARD WHILE THE CLOUD TOP TEMPERATURES
HAVE BEEN WARMING DURING THE PAST FEW HOURS. A FRAGMENT OF A BAND
LIES TO THE SOUTHEAST OF THE CENTER...BUT IT TOO IS BEING SUBJECTED
TO STRONG SHEAR OF ABOUT 30 KT ACCORDING TO SHIPS/UW-CIMSS
ANALYSES. NEVERTHELESS...A MORNING ASCAT PASS INDICATED AT LEAST
40-KT WINDS ABOUT 60 N MI NORTH OF THE CENTER. DESPITE THE
DEGRADATION OF THE CLOUD PATTERN IN RECENT HOURS...THE INITIAL
INTENSITY IS RAISED TO 40 KT BASED ON THE ASCAT PASS.
SEVERAL SMALLER-SCALE VORTICES HAVE BEEN ROTATING AROUND THE MEAN
CIRCULATION CENTER OF HUMBERTO TODAY...MAKING AN ESTIMATE OF THE
INITIAL MOTION MORE DIFFICULT THAN NORMAL. A LONG-TERM AVERAGE OF
FIXES SUGGESTS A MOTION OF 300/05. THE TRACK PHILOSOPHY IS NO
DIFFERENT THAN EARLIER. HUMBERTO IS FORECAST TO MOVE SLOWLY
NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD FOR THE NEXT COUPLE OF
DAYS INTO A COL REGION IN BETWEEN A MID-LEVEL RIDGE OVER THE
NORTHEASTERN ATLANTIC AND A MID-LATITUDE SHORTWAVE TROUGH OVER
ATLANTIC CANADA. IN ABOUT TWO DAYS...THE CYCLONE SHOULD UNDERGO
RECURVATURE AND ACCELERATE WHEN THE AFOREMENTIONED TROUGH
APPROACHES FROM THE WEST. THE NEW NHC TRACK FORECAST CONTINUES TO
LIE CLOSE TO THE MULTI-MODEL CONSENSUS TVCA...IN BETWEEN THE
MORE-WESTERLY GFS AND THE MORE-EASTERLY ECMWF MODEL SOLUTIONS.
THE SHEAR OVER HUMBERTO IS STILL FORECAST TO DECREASE SOME DURING
THE NEXT COUPLE OF DAYS AS A MID- TO UPPER-LEVEL TROUGH NORTHWEST
OF THE STORM SHIFTS EASTWARD. THE RELAXATION OF SHEAR AND WARMER
WATERS ALONG THE FORECAST TRACK SUGGEST AN OPPORTUNITY FOR SLOW
STRENGTHENING IN THE SHORT TERM. AFTER THAT TIME...THE INTERACTION
OF HUMBERTO WITH A SHORTWAVE TROUGH IN THE WESTERLIES SHOULD ALLOW
A FASTER RATE OF INTENSIFICATION UNTIL EXTRATROPICAL TRANSITION
OCCURS BETWEEN DAYS 4-5. THE NHC INTENSITY FORECAST IS A BLEND OF
THE HIGHER SHIPS OUTPUT AND THE LOWER INTENSITY CONSENSUS AIDS/LGEM
THROUGH 48 HOURS AND CLOSE TO A BLEND OF ALL THE GUIDANCE AT LATER
TIMES.
FORECAST POSITIONS AND MAX WINDS
INIT 16/2100Z 27.3N 43.5W 40 KT 45 MPH
12H 17/0600Z 28.4N 44.0W 40 KT 45 MPH
24H 17/1800Z 29.5N 44.9W 45 KT 50 MPH
36H 18/0600Z 30.4N 45.4W 50 KT 60 MPH
48H 18/1800Z 31.2N 45.6W 50 KT 60 MPH
72H 19/1800Z 33.5N 44.3W 60 KT 70 MPH
96H 20/1800Z 38.0N 40.0W 65 KT 75 MPH
120H 21/1800Z 47.0N 30.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
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FORECASTER KIMBERLAIN
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